Most larger transactions are handled by large commercial real estate firms that cap their commissions at a $100K or so on multi-million dollar properties.
Not even remotely true...
Suppose it might depend on what world one might live in.
I'm sure you could find a realtor that would charge you $1.5M to sell a $30M property but there are hosts of commercial firms that cap their commissions at realistic rates.
Many multi million dollar properties are doing good to even have 10 to 15% of equity in them, nobody is going to split their total proceeds from a sale with a realtor just because they brought a buyer to the table..